Diesel Place banner
1 - 16 of 16 Posts

·
Registered
Joined
·
2,161 Posts
Discussion Starter · #1 ·
Is the programming in the TCM different or not in the TCM for a 8.1L or Duramax of any given year (Say 2003 8.1/6.6 or 2006 8.1/6.6)? If it's the same, does it base the shift points off information from the ECM?
 

·
Registered
Joined
·
892 Posts
Typically the programs change every year. Sometimes, like in MY01 and MY02, there are also service releases.

The Allison bases the shift pattern on engine torque or throttle (from the engine module) and output speed at the trans.
 

·
Registered
Joined
·
2,161 Posts
Discussion Starter · #3 ·
Typically the programs change every year. Sometimes, like in MY01 and MY02, there are also service releases.

The Allison bases the shift pattern on engine torque or throttle (from the engine module) and output speed at the trans.
So you could take a TCM from a truck with the 8.1, install it ina truck with the Duramax, and it should shift right?
 

·
Premium Member
Joined
·
20,556 Posts
yeah, ive been wondering too....because the 2006 8.1 ECMs as far as I know, are the old 16-bit ECM's that the 2001-2005 Duramax runs. That proves that the old generation ECM's have the capability to communicate on a J1939 CAN/databus level with the older ECM's...

--Ben
 

·
Registered
Joined
·
2,161 Posts
Discussion Starter · #5 ·
yeah, ive been wondering too....because the 2006 8.1 ECMs as far as I know, are the old 16-bit ECM's that the 2001-2005 Duramax runs. That proves that the old generation ECM's have the capability to communicate on a J1939 CAN/databus level with the older ECM's...

--Ben
Remeber the Duramax ECM changed for the LLY... I THINK the 2001-2004 had two long connectors like the 8.1 ECM, but the LLY ECM has three connectors (But you know that already ;) ).
 

·
Registered
Joined
·
892 Posts
No, you could never exchange a Duramax program with a 8.1L. The Duramax uses J1939 (which changed to GMLAN for MY06) and Class II for communication. The 8.1L only uses Class II.

Both the Allison and the Duramax have new controllers for MY06.

Now, you can exchange a 8.1L 3.73 axle program with a 8.1L 4.10 (and vice versa) but your shift points will be off.
 

·
Premium Member
Joined
·
20,556 Posts
ahhh!! I knew the LLY and LB7 PCM's were different in terms of connectors etc.. but I did not know the 8.1 ECM's were so similar to the LB7 ECM's. That shouldnt matter tho, right? Its only a connector change...in terms of data busses, communication, the LB7 and LILLY ECM's are identical. So for the LILLYs youd need to change some pins around...

--Ben
 

·
Premium Member
Joined
·
20,556 Posts
The 8.1L only uses Class II.
how is Class II even close to being fast enough for ECM-to-TCM communication on the 8.1?? I thought its data rate was only like 12k/sec or soemthing slow like that (not as slow as E&C tho!). And I thought that was one of the reasons for implementing J1939 on the Dmax....it needed soemthing FAST to talk to the TCM with. THis wasnt an issue on teh gassers because the trans is controlled by the ECM (or rather 'PCM'). The 8.1 ECM would still need a much fatser means of communication than Class II I would think...

--Ben
 

·
Registered
Joined
·
2,161 Posts
Discussion Starter · #9 ·
No, you could never exchange a Duramax program with a 8.1L. The Duramax uses J1939 (which changed to GMLAN for MY06) and Class II for communication. The 8.1L only uses Class II.

Both the Allison and the Duramax have new controllers for MY06.

Now, you can exchange a 8.1L 3.73 axle program with a 8.1L 4.10 (and vice versa) but your shift points will be off.
Ok... Makes sense. Back to the drawing board (Crawls back into hole)...
 

·
Premium Member
Joined
·
20,556 Posts
I just checked SI...the 8.1 ECM did NOT chnage for the 2006 MY according to GM
 

·
Premium Member
Joined
·
20,556 Posts
SO machinator you're saying the 2006 8.1 TCM is totally different than the 2006 Dmax TCM?
 

·
Registered
Joined
·
892 Posts
The TCM for the MY06 Duramax and 8.1L is physically the same, but the programs are different. The 8.1L and Duramax engine controllers are completely different and always have been.

Now, just to recap: The MY06 TCM and Duramax ECM are completely different from the MY01-MY05 TCM and Duramax controllers but the 8.1L controller is the same for MY01-MY06.

The 8.1L does run on Class II and it is slow. But, as it is much simpler of an engine than the Duramax it work just fine. However, those items in the 8.1L that do require a faster broadcast rate (such as the torque management) have their own dedicate wires to the TCM.
 

·
Premium Member
Joined
·
20,556 Posts
The TCM for the MY06 Duramax and 8.1L is physically the same, but the programs are different.
Perfect thanks...thats what I needed to know.

but the 8.1L controller is the same for MY01-MY06.
Thanks...that was also information that I needed to confirm.

The 8.1L does run on Class II and it is slow. But, as it is much simpler of an engine than the Duramax it work just fine. However, those items in the 8.1L that do require a faster broadcast rate (such as the torque management) have their own dedicate wires to the TCM.
Didnt know that! Now I do...thanks. I always thought realtime data like VSS information could not be transmitted over Class II simply because its too slow. Which is why on Escalade TNR nav units, they have a dedicated VSS line going into them, whereas the 6-disc changer radios (which need VSS data to operate the speed compensated volume) just picked up VSS data thru the data bus, but this was too slow for the real time VSS data that the nav units need, thus its requirment for a dedicated VSS input.

Heres another question...which is what im really getting at. Does a MY03-05 Dmax ECM have a chance in the world of ever communicating with a Gen IV TCM?

--Ben
 

·
Registered
Joined
·
892 Posts
The simple answer is yes, but it is not feasible unless you have someone who can rewrite both the TCM and ECM code to get the two to talk nicely with eachother. Eventhough J1939 and GMLAN are very similair, there is enough of a difference in the messaging to cause a no-go situation.

Getting the mechanical parts to turn a pre-MY06 into a six-speed is fairly easy. It's always been the software side of the conversion that makes it virtually impossible.
 

·
Premium Member
Joined
·
20,556 Posts
The simple answer is yes, but it is not feasible unless you have someone who can rewrite both the TCM and ECM code to get the two to talk nicely with eachother. Eventhough J1939 and GMLAN are very similair, there is enough of a difference in the messaging to cause a no-go situation.

Getting the mechanical parts to turn a pre-MY06 into a six-speed is fairly easy. It's always been the software side of the conversion that makes it virtually impossible.
bahhh!!!!:mad: Not the answer I was looking for....but its the answer I was afraid of...:rolleyes:

Thanks Machinator

--ben
 

·
Registered
Joined
·
235 Posts
Good discussion!

Ben,
I received that CD some time ago. THANKS! However, I haven't spent any time looking over the information. ... why I promise to do things I think I will get to but realistically know I probably never will is still beyond me ... thanks anyway! I'll attempt to make an effort to spend some "at home" engineering time. I probably owe you a beer or something ...

I have to tablize the information here ... take a look and make sure I'm correct.

Text Font Number Line Design

So, what we're missing in the "8.1L ECM talks to the GenIV TCM, so why can't the GenIV TCM talk to the pre-'06 Duramax" topic is the data communicated over the J1939 link on the pre-'06 Duramax trucks, right? Follow me? Do we know what signals/data are communicated over J1939?

I'm probably not helping. I think Machinator is right, this is a matter of getting the pre-'06 ECM to talk with the GenIV TCM which will require software (or some relay/translator module inbetween if possible) work to make this possible.

Ben & Cougar - thanks for keeping "the convert the 5-speed to 6" topic alive. It sure is interesting and I've learned a lot over the past several months discussing this.
 
1 - 16 of 16 Posts
Top